Abstract: The infrared target simulation system based on the digital micromirror device (DMD) has the advantages of high resolution, high frame rate and large temperature range, which can detect and evaluate the working performance of the infrared detection system economically and effectively. In order to study the influence of the structure design for illumination system on the imaging uniformity and reduce the illumination uniformity of the image surface in the infrared target simulation system based on the DMD, a method to eliminate the imaging nonuniformity was proposed. In which the structure parameters of the DMD illumination system were analyzed and designed, the ratio of the imaging beam cross-sectional area was taken as the relative illumination index, the mathematical model was established with the software for numerical simulation, and the structure parameters which could eliminate the illuminance nonuniformity caused by the vignetting was obtained. The relative illuminance distribution of each point on the image plane was ranged from 8.75%~1; the results of the theoretical analysis were verified by the TracePro, and the relative illuminance distribution of each point on the image plane was ranged from 90.91%~1, which was consistent with the theoretical analysis results. It was proved that in the case of the rational design of the structure parameters for DMD illumination system, the image plane illuminance nonuniformity caused by the vignetting could be reduced effectively, which provided a reference for the design of structural parameters for infrared target simulation system and image plane illuminance analysis.